Thank you, @bwiernik . That's an interesting solution...I will try it. Although this could become a lot of work if one has many such books with section items.

Is there any way this might be implemented more directly in a future Zotero version? Essentially it would be something like an "alias" feature for the PDF.

Just as an item can appear in multiple Zotero collections, without duplication of the item, this would mean that an attachment could appear in multiple Zotero items without duplication of the actual attachment file.

As is, this seems to be a "pro" in favor of using linked attachments rather than storing attachments in Zotero database.

"Overthinking" is my modus operandi, for better or worse. Hence the appeal of a system like Zotero to organize ideas, research, optimize new way of working; I am still learning the ins and outs of Zotero. I'll explore the Related Items approach. Thank you again for all the suggestions and explanations.

There are two different logics at work here, which is why the solution can only be a compromise. Zotero operates on a logic of citation: its primary units are citable entries. In a collection of contributions by different authors, or of papers by the same author, that's the chapter, and the consistent approach is to break up the pdf-file and attach the chapters exclusively to the chapter-entries. But of course publishing houses don't, as a general rule, publish single chapters: they follow what I think of as a logic of the bookshelf and publish books, with general introductions and sometimes general bibliographies and indices as well. Ideally, one would want a way of representing that within Zotero as well, but since collections are not, as a rule, first-level citable items, Zotero will allow you to make an entry for them but the software is thinking in the background, hey, what is the point?

My own approach varies wildly. Usually I do the related items thing, because I'm short on time and can't be bothered splitting a pdf of a whole collection up. But I agree that this is suboptimal: I would like to be able to tell by just looking at a book chapter in the main window whether I have the text or not, but there's no way to represent that without the need to click something, and I don’t want more than one copy of things (otherwise the annotation problem you mention arises almost of necessity). Ideally, I would take the time and make individual pdfs of the chapters, one by one, and link them all to individual chapter entries. I would then make a separate entry for the introduction, and attach only the bibliography and index to an entry for the whole book.

@ZenonMarko: To extract pdf bookmarks, use Zotfile's "Manage Attachments" -> "Get Table of Contents" from the item's context menu. This will add a linked table of contents to the note that is shown when the pdf attachment is selected in the middle pane. If you need to create a large number of bookmarks, PDFtk has some text-based tools that might be useful, see here.

If you have a complete book attached to a book item, you could add a URI attachment to a related book section that links to zotero://open-pdf/library/items/[itemKey]?page=[page], using the Attachment menu. You get such links from extracting bookmarks or comments. (Zutilo's "Copy select item links" function can help with getting the itemKey. Also note that stored files are saved to /Zotero/Data/storage/[itemKey]/[filename].) Currently, though, double-clicking the parent book section item will not open such a URI attachment if the item has a URL, DOI, or another pdf or file attachment. It is planned to add an option to set the primary attachment for an item, see https://github.com/zotero/zotero/issues/1715. Given this example, it would be nice if one could also set an attached URI link as the primary attachment.

@gpatten Thank you for that. Sorry I didn't reply to your detailed comment at the time, which mirrors my thinking thus far.

I've thus far been using the related items approach as follows:

- create single book Zotero item with the anthology attached as PDF; add editors to item info

- make sure the PDF has bookmarks for chapters, named by the chapter title and author

- Manage Attachments: Get Table of Contents

- use Zutilo: Create Book Section just for the chapters (different author articles) of interest (that is: ones I might read and cite)

- manually add in author and title info for the Book Section item

- copy the URI link from the parent item PDF Table of Contents

- paste that URI link into the Book section item using contextual menu command: Add Attachment: Attach Link to URI (or assign a keyboard shortcut in Zutilo; I use Command-Option-U on Mac)

Yes, that algorithm entails many steps, and becomes quite time-consuming for a large # of anthologies and chapters.

The good news: if one double-clicks on the chapter item, the PDF opens to the correct page of that chapter (assuming the PDF has proper pagination, and PDF reader is set correctly, etc.... beware the settings for Logical page #s and whether the PDF has indeed 2 sets of page numbers).

Some Pros(+) / Cons(-) of this approach:

(+) no need to split up the PDF
(+) entire anthology PDF is searchable
(+++) only create chapter items for those chapters of interest, as needed, rather than cluttering up my Zotero database (sometimes there is only one immediately relevant article/chapter from the anthology)
(-) no way to just search the PDF of a chapter; any searches for a keyword will search the entire PDF

If anyone has ideas on a more elegant solution, please do join the fun here!

Feature Request:
In the attachment menu, add a "Add Link to existing Attachment..." option asking for an attachment (select from existing ones in zotero) and an optional page number (perhaps be able to browse the PDF directly) to automatically create a link like @qqbb provided
zotero://open-pdf/library/items/[itemKey]?page=[page]

Thereby one would not have to look up the itemKey.

This could be automized or pre-filled if the book already exists and is linked to the book chapter.

I like ben.meiers suggestion a lot. Theres already an option to link to websites, why not make it possible to link to PDFs within zotero. That's my main issue with related items anyways, that I can't double click on the chapter and the PDF opens. Link to attachment already exists, but it doesn't include the annotations from the main book.